Northampton South Conservatives Association has admitted an administrative error led to an unregistered donation of £10,000 to the fighting fund of David Mackintosh.

An inquiry is understood to have been started by Conservative Party central office into the registration of one of those payments with the Electoral Commission. This payment is understood to have been registered only last week due to an administrative error.

Councillor Suresh Patel, the chairman of Northampton South Conservatives and Mr Mackintosh’s election agent, told the Chronicle & Echo he had been made aware of the unregistered payment late last week.

“This was an administrative error which we found about last week. As soon as we were aware, we contacted the Electoral Commission and I understand it has now been registered officially,” he said.

Councillor Patel said the party locally had contacted Conservative Party Central Office which had confirmed they were investigating the situation.

Following approaches by the Chronicle & Echo to Mr Mackintosh and Conservative Party Central Office yesterday, a spokesman for the Northampton South MP said this afternoon: “All donations and hospitality have been correctly declared in line with Electoral Commission rules, save one donation in April 2014. This is in the process of being rectified.”

Mr Mackintosh was elected as the Northampton South MP in May this year. In July 2013, he announced his intention to stand as a candidate after Brian Binley announced his decision to stand down.

Mr Mackintosh was leader of the Northampton Borough Council when the £10.25 million loan deal was agreed with Northampton Town. The club appointed 1st Land Ltd to carry out the stadium redevelopment work. The sole director of 1st Land was Howard Grossman.

The unregistered donation to Northampton South Conservative Association was made by businessman Gary Robert Platt. A search on Companies House shows Mr Platt was listed as a director at County Bideford Limited along with Howard Grossman. Mr Platt had no involvement with 1st Land.

The Chronicle & Echo has not been able to contact Mr Platt for comment.

There were other election campaign payments to Northampton South Conservative Association listed with the Electoral Commission last year.

None of those payments were made by any individuals connect to the company, 1st Land. There is nothing illegal about individuals or businesses giving donations to political candidates for election funds and all donations are registered with the Electoral Commission and approved by political parties. There is no suggestion that there was anything wrong with the payments made to the election fund.

One payment was from Al Mayfield, the owner of Great Events Etc. Mr Mayfield was on the organising committee of the Amy Winehouse Foundation Ball, a charity ball held in November 2013 to raise money in memory of the pop star. Also on the organising committee was Mr Grossman and members of the Grossman family.

Mr Mackintosh had received a free ticket to the ball courtesy of County Group, of which Mr Grossman is a director. This ticket had been declared under the ‘gifts and hospitality’ section on Northamptonshire County Council’s website but is not listed on the borough council website. It is understood that it was registered at the time with both the borough and the county council

When approached by the Chronicle & Echo yesterday, Mr Mayfield said it was a matter for him as to who he gave money to but declined to comment further.

Mr Grossman’s spokesman said Mr Grossman could not comment on the election campaign payments as they had not been made by him.

A report by the BBC’s regional investigations team this morning has also given details of a payment by Howard Grossman of £6,185 for tickets to a fund-raising dinner organised by Mr Mackintosh at the Carlton Club in London as part of the election campaign.

Mr Grossman’s spokesman added: “Howard Grossman paid £6,195 for tickets to attend an event hosted by Mr Mackintosh as part of his election campaign. A number of other political figures attended the event.”